Laparoscopic, endoscopic, and other minimally invasive surgical techniques enable surgeons to perform fairly complicated procedures through relatively small entry points in the body. The term “laparoscopic” refers to surgical procedures performed on the interior of the abdomen, while the term “endoscopic” refers more generally to procedures performed in any portion of the body. Endoscopic surgery involves the use of an endoscope, which is an instrument permitting the visual inspection and magnification of a body cavity. The endoscope is inserted into a body cavity through a cannula extending through a hole in the soft tissue protecting the body cavity. The hole is made with a trocar, which includes a cutting instrument slidably and removably disposed within a trocar cannula. After forming the hole, the cutting instrument can be withdrawn from the trocar cannula. A surgeon can then perform diagnostic and/or therapeutic procedures at the surgical site with the aid of specialized medical instruments adapted to fit through the trocar cannula and additional trocar cannulas providing openings into the desired body cavity.
Some known advantages of minimally invasive surgical techniques include reduced trauma to the patient, reduced likelihood of infection at the surgical site, and lower overall medical costs. Accordingly, minimally invasive surgical techniques are being applied to an increasingly wider array of medical procedures.
Many surgical procedures require body vessels to be ligated during the surgical process. For example, many surgical procedures require cutting blood vessels (e.g., veins or arteries), and these blood vessels may require ligation to reduce bleeding. In some instances a surgeon may wish to ligate the vessel temporarily to reduce blood flow to the surgical site during the surgical procedure. In other instances a surgeon may wish to permanently ligate a vessel.
Vessel ligation may be performed by closing the vessel with a ligating clip, or by suturing the vessel with surgical thread. Performing vessel ligation using surgical thread requires complex manipulations of the needle and suture material to form the knots required to secure the vessel. Such complex manipulations are time-consuming and difficult to perform, particularly in endoscopic surgical procedures, which are characterized by limited space and visibility. By contrast, ligating clips are relatively easy and quick to apply. Accordingly, the use of ligating clips in endoscopic surgical procedures has grown dramatically.
Ligating clips may be classified according to their geometric configuration as either symmetric clips or asymmetric clips, and according to the material from which they are manufactured. Symmetric clips are generally “U” or “V” shaped metallic clips that are substantially symmetrical about a central, longitudinal axis extending between the legs of the clip. By contrast, asymmetric clips lack an axis of symmetry. For example, U.S. Pat. No. 4,834,096 to Oh et al. describes a polymeric, asymmetric surgical clip in which a first leg member includes a lip that mates with the second leg member to lock the clip in place. Asymmetric clips have certain advantages over symmetric clips. For example, because asymmetric clips are formed from polymeric materials, the mouths of asymmetric clips can be opened wider than the mouths of symmetric clips. This allows a surgeon to position the clip about the desired vessel with greater accuracy. In addition, a clip of the type described in U.S. Pat. No. 4,834,096 can be repositioned before locking the clip on the vessel, a process referred to as “approximating” the clip, or to be removed from the vessel.
Ligating clips are applied using mechanical devices commonly referred to as surgical clip appliers, ligating clip appliers, or hemostatic clip appliers. Surgical clip appliers adapted for endoscopic surgical techniques include a shaft adapted to be inserted through an endoscopic cannula to access a surgical site in a body cavity and a jaw assembly disposed at the distal end of the shaft for retaining a surgical clip. In use, the clip is positioned over the desired vessel and the jaw is actuated, typically using a mechanism disposed in the handle of the device, to close the clip about the vessel.
Multiple clip applier systems have been developed that enable surgeons to deliver multiple symmetric surgical clips to an endoscopic surgical site. In general, these systems provide a surgical clip channel within the shaft of the device and a mechanism for delivering the surgical clips through the shaft to the jaw assembly. For example, U.S. Pat. Nos. 5,100,420 and 5,645,551 to Green et al. describe a device for delivering and applying multiple surgical slips to an endoscopic surgical site. Similarly, U.S. Pat. No. Re 35,525 to Stefanchik et al. aims to provide an endoscopic multiple ligating clip applier with a venting system. U.S. Pat. No. 5,700,271 to Whitfield et al., European Published Patent Application No. 0 409 569 A1, and European Patent No. 0 596 429 B1 propose other clip applier designs.
As endoscopic techniques have been developed, certain inadequacies in the available surgical equipment have become apparent. For example, the jaws of the applier, which are typically used to close a clip around a vessel, may exert unequal pressure on the clip, resulting in a “scissoring” effect and damage to the vessel. In other instances, the clip may not be properly oriented when it is placed within the jaws or may slip out of alignment during application. This may result in the loss or misapplication of the clip. In still other instances, the applier may jam or may simply fail to deploy a clip.
Furthermore, existing multiple clip applier systems have been designed for symmetric clips and are not well suited to satisfy design issues unique to asymmetric clips. For example, symmetric clips can be retained in clip jaws by holding opposing surfaces of the clip's legs in opposing channels. By contrast, asymmetric clips cannot easily be retained in opposing channels because the clip's legs deform when the clip is closed. In addition, when symmetric clips are closed on a vessel, the opposing legs of the clip apply substantially even pressure to the opposing sides of the vessel. By contrast, the opposing legs of an asymmetric clip may apply varying pressure to opposing sides of a vessel when the asymmetric clip is closed. Moreover, locking asymmetric clips of the type described in U.S. Pat. No. 4,834,096 function best when force is applied at or near the distal ends of the clip legs. Still further, asymmetric clips of the type described in U.S. Pat. No. 4,834,096 may need to be placed under compression to be retained in the clip channel. Thus, conventional clip advancing mechanisms designed for symmetric clips may not reliably advance asymmetric clips. In addition, conventional clip advancing mechanisms designed for symmetric clips may not provide the ability to approximate a clip.
Therefore, conventional clip appliers designed for symmetric, metal clips suffer from certain deficiencies and are not adapted to deliver asymmetric, polymer based clips. Accordingly, there is a need to provide an endoscopic clip applier that can reliably deliver a sequence of clips and in a manner which minimizes the risk of damage to the vessel. Additionally, there is a need for an endoscopic clip applier adapted to deliver asymmetric, polymeric ligating clips.
The foregoing problems have been addressed in whole or in part by an endoscopic clip applier adapted for delivering asymmetric, polymeric clips disclosed in copending, commonly assigned U.S. patent application Ser. No. 09/905,679, published as U.S. patent application Publication No. US 2003/0014060 A1, the content of which is incorporated herein in its entirety. In the use of such clip appliers, it has been found that difficulties may sometimes arise when attempting to release an applied clip from the jaws of the clip applier. Specifically, in some instances, clips may tend to become caught or hung up in the jaws in a manner that impedes their easy release therefrom. The subject matter disclosed herein is provided to address this issue.